1. Field of the Invention
One disclosed aspect of the embodiments relates to image pickup apparatuses having a plurality of pixels containing a plurality of photoelectric conversion units.
2. Description of the Related Art
In recent years, an image pickup apparatus having pixels containing photoelectric conversion units has been required to carry out quick signal output.
For example, an image pickup apparatus has been known which includes pixels which perform photoelectric conversion and output signals based on incident light and a column parallel analog-digital converting circuit having an AD converter at each column of a pixel array in which pixels are arranged in matrix form. Hereinafter, an analog-digital converting circuit will be called an ADC. A column parallel ADC will be called a column ADC. In the column ADC, analog-digital conversion (hereinafter, called AD conversion) is performed in which a control unit of each column converts an analog signal output from a pixel to a digital signal. (Hereinafter, an analog signal output from a pixel will be called a pixel signal).
On the other hand, Japanese Patent Laid-Open No. 2001-83407 discloses an image pickup apparatus which has a plurality of photoelectric conversion units for each microlens of a two-dimensionally arranged microlens array and performs focal point detection by phase difference detection. It further discloses that a signal based on a signal charge of a first photoelectric conversion unit of a plurality of photoelectric conversion units, a signal based on a signal charge of a second photoelectric conversion unit that is different from the first photoelectric conversion unit, and a signal based on a signal charge combining the first photoelectric conversion unit and the second photoelectric conversion unit are output.
Japanese Patent Laid-Open No. 2002-320146 discloses a configuration in which pixels are arranged in matrix form, signals output from different pixels are added and the added signal is output to an operational amplifier. Japanese Patent Laid-Open No. 2002-320146 discloses a configuration having an operational amplifier at each column of pixels. Furthermore, in an image pickup apparatus according to Japanese Patent Laid-Open No. 2002-320146, an operational amplifier at one column and a noninverting input terminal (−) of an operational amplifier of a neighboring column are connected via a switch. This allows addition of signals of pixels of neighboring columns and output the added signal to an operational amplifier.
The image pickup apparatus of Japanese Patent Laid-Open No. 2001-83407 does not consider quick conversion of at least two analog signals output pixels to digital signals.
Japanese Patent Laid-Open No. 2002-320146 does not sufficiently consider quick conversion of at least two analog signals output from pixels of a plurality of columns to digital signals.